I have two Cateye HL-EL135Ns that are on blinking mode while I ride during the day for oncoming traffic visibility, so I think using the strobe on the S2+ during the day would be ideal, but care to point it down once the sun starts to set.
As for the 10197, after reading garrybunk's thread on diffusing techniques I definitely wanted to have a 30*60 wide beam. If you're in the states, LEDSupply has them for $1.25 shipped w/ tracking, otherwise Intl-Outdoor has them in a 2-pack for $2.65.